15K vs 13.5K A/C

[LandJ]

I'm getting close to ordering our new trailer, and I thought I was going to get the 15K for sure. Now I'm doubting myself...

The trailer is a Rockwood 2604 and the reasons I'm not sure are:

1) Will my Honda 3000 be able to run it?

2) Will it run on a 20A circuit while parked at my house?

I know the 13.5 will, cause I have that now.

Need some opinions... Thanks

[HookupAndGo]

I had a 15K on my TT (now have a MH). Problem that I always seemed to deal with was just the amount of amps vs the benefit. We always seemed to have to really monitor things. Running on a 20A breaker it can be close.

[dj3spots]

Our 15k won't run on house power. We have a dedicated circuit just to keep RV plugged in. Never tried the 13.5 gonna have to try that.


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[BigPatCal]

I opted for the 15K - works like a charm. Less work for the unit to keep trailer cool, esp with just 1 AC unit. Very happy I did it. It was short $ compared to doing it later.

[aceinspp]

I'd go for the 15000 BTU as if you come south you will be glade you did. Depending on the num of slides it will take more to cool the TT. Later RJD

[Herk7769]

Go big or go home.

Unless you run your air conditioner (A LOT) off a generator (the 15k uses more juice to get started), you will be happy you got the upgrade.

[Tinmania]

1.) It should start and run it if plugged into the the generator's 30A outlet. But not at higher altitudes. Once started you probably will only have about 500-700 watts of spare power, so won't be able to run much else.

2.) If there is nothing else in the house using the 20A circuit and the cord to connect to the RV is heavy enough and not overly long, it should run it. I wouldn't plan on running much else, however.



Mike

[Saubleguy]

Run my 15k at home on 15amp circuit - no prob. Using #12 extension cord wire to feed it.

[Herk7769]

Originally Posted by Saubleguy

Run my 15k at home on 15amp circuit - no prob. Using #12 extension cord wire to feed it.

I have to say that I believe you are seriously overloading that extension cord and may have damaged your 15 amp breaker from over heating.

Humor me and plug in a voltage tester (and an ammeter if you have a "Kill-a-Watt) at the junction of your #12 extension cord and your camper's shore power cord. Test again inside the camper.

Let me know what your startup voltage drops to and the highest amperage recorded. You can calculate the amps by dividing the recorded start up wattage by the lowest volts recorded.

I would not be at all surprised to find you are looking at 28 - 35 instantaneous amps on that cord and breaker after the voltage drop on the way to the camper.

Humor me and let me know...

I will take a video of my Coleman Mach III 15K starting up. I have a hard wired AC voltmeter and ammeter right at the socket entrance of the camper.

I feed my house power camper circuit off of a dedicated 20 amp breaker with 25 feet of #12 exterior grade ROMEX to the TT socket; then I plug the camper cord directly into it. I think you will be surprised with the result.

[conceptumator]

Our old RV was 30A with a 4KW generator. We pulled out the original 13.5KW AC unit and replaced it with a new Dometic 15KW and never had an issue. Really made a huge difference, though I can't speak to how much of the difference was the size of the unit versus how lousy the older unit may have been functioning.

[Herk7769]

OK, so I apologize for the video quality, I was in a hurry.

I think I will do it again with better lighting and the fridge off (I don't know if it was cooling or the converter was still charging my battery.) The "null state" was 2.7 amps and 116 volts.

First a little about the mods I did to my AC to get the start up Current DOWN to the observed amps 24.9 - Subtract 2.7 to what you see on start up and run so there is a comparison.

I installed a Hard Start capacitor in both the Fan Motor and the Compressor; then I added a delay relay so the compressor starts first followed by the fan about 5 seconds later. You can hear the compressor lug and the amps shoot up as the line voltage drops. Shortly later the blower starts peaking again at 17 amps as it comes online. Once both are on speed you can see the "running amps."

Before the mods I had typical startups around 29 amps that kicked my 3500 watt inverting generator off line.

I have a new CB and 10 gauge wire to upgrade my trailer socket to a full 30 amps to keep the voltage drop down when I run the AC.

https://www.youtube.com/watch?v=ri4IYaStLfk

[LandJ]

Sounds like the 15K is too much for a Honda 3000. My dealer told me Dometic recommends a 3.5KW generator.

[LandJ]

Seems the dealer might not have good info... Dometic also recommends 3.5KW generator for the 13.5K unit as well. The running amperage is only .8A more for the 15K. Doesn't give a spec on startup current.

[Herk7769]

Look at the manufacturer's plate on the AC for a "fair" idea what the start up amperage will be. Look for something called LRA

That is Locked Rotor Amps or the amount of amps the compressor motor will pull at a dead stop. Once it starts turning the amps will drop to its operating amperage.

Column-by-Column: Locked Rotor Amps and KVA | Franklin AID

My LRA is 58 amps but the compressor will begin to turn almost immediately and my ammeter display is not instant so I get an average over the 1 second sample time.

RLA: Acronym for "rated load amps". The maximum current a compressor should draw under any operating conditions (running on speed). Often mistakenly called running load amps which leads people to believe, incorrectly, that the compressor should always pull these amps. You should never use the listed RLA to determine if the compressor is running properly or to condemn a compressor. The running amps of a compressor are determined by the evaporator temperature, condensing temperature and the line voltage.

FLA - Full Load Amps: Changed in 1976 to "RLA - Rated Load Amps".

That is why some folks have no trouble with their generator and others can't get it to go. Air temp, humidity, and line voltage play a big role in whether your Generator can turn the beast over.

Some generators are more sensitive to overload than others as well and may drop off line quicker than others.

[BusyRetirees]

We had a 2013 Rockwood 8265ws with the 13.5 AC. We now have a 2014 Rockwood 8282ws with 15 AC. Glad we upgraded to the 15 AC. Cooled the whole unit down in a timely fashion. The 13.5 had to struggle and took a bit of time cooling the unit down.

[Big Vic]

I have a 15K in my 2604. It works great in cooling both the bedroom and rear living area. I run it with two Honda eu2000s. My Progressive Industries monitoring system states that it pulls about 18 amps. 18ampsx120v = 2160 watts. Your 3000 should be fine, but you won't be able to run the microwave, water heater or coffee maker at the same time.

[Tinmania]

Originally Posted by LandJ

Seems the dealer might not have good info... Dometic also recommends 3.5KW generator for the 13.5K unit as well. The running amperage is only .8A more for the 15K. Doesn't give a spec on startup current.

I have a Dometic 13.5 and it runs no problem with my Yamaha ef2800i inverter generator (2800w surge, 2500w rated). I can even run my Microwave at the same time if the AC is already running.

I have used that generator for hours at a time in 115 degree heat here in Arizona and no issue with the AC other than it struggles to keep things cool. I have an extra teen in the house for the summer and I work at home. So I have been using the RV as my office during the week. The voltage drops enough from grid power in this heat to the point I don't want to trust my 15A circuit to run the AC (the AC itself is on a 15A circuit and when I run it connected to my home it is the only thing running on AC). So I use the generator for those hours and there has never been a problem

I can't see the 3000w honda being any different with a 15k AC.



Mike

[LandJ]

Here's the answer I got back from the dealer....

Yes they do. There is only about 1amp difference between the two when running. The generator recommendation is because of startup. When the compressor starts on a 15k it momentarily draws about 66amps (13.5k about 63amps). If using a smaller generator it may not be able to handle this spike in demand and could damage the AC compressor.

There is only a slightly noticeable difference between the 13.5 and 15k. We normally stock 13.5k on all travel trailers under 35 ft. We option the 15k on anything over 35 feet and all 5th wheels and park models.

[LandJ]

I went with the 13.5K. I don't want to have problems with my generator. I can always upgrade later if it's not enough.

Thanks for the help.

[B and B]

I run a 4 kw (4.5 kw surge, 3900 running watts) Generator with my 15K no problems. Remember depending on generator model a Honda 3100 is only 2800 running watts with a 23.8 amps maximum current capacity.